How to store WTForm Form in session in Flask?
You can cast the date and decimal as a string before storing it in the session. Then use strptime to convert the datetime from the string in session back to a date when you need to access it, and Decimal to convert the decimal values. It feels like a kludge to me with having to assemble the dictionary for session and recasting those values as strings, but with the limitations of serializing, I don't know of a better way.